Looking for a quick way to learn the basics of XML? Well, this site will give you a Kickstart!

This set of tutorials covers XML and just about every related technology. ZVON tutorials, in the HeadGeeks humble opion, are great. They have kind of a cult following, not to mention a bunch of examples.

Project Cool teaches people - primarily web designers and developers - not programmers, how to build web pages. Now they've gone into XML. Cool!

The Developer Zone. A very easy to follow and nicely organized tutorial on XML and more..

From the makers of the XML School. This site is a well organized tutorial on Schema (a replacement for DTD?) with lots of working examples and source code.

XML for nearly anyone. XML not another obstacle, but a way around obstacles

Actually it took me about 12 minutes, but I am a slow reader :)

The Developer Zone. A very easy to follow and nicely organized tutorial on XML and more

A comprehensive list of links for XML Tutorials

Tutorials on using XML and XSL for GUI development

Full-day XML Tutorial

Tutorial: XML and Perl: Embedding XML in HTML

Site shows how to get an XML document to Adobe PDL (via LaTex)

Using simple, well-explained examples this tutorial walks you through XML and the sister XSL style sheet language

OmniMark has an unrivalled heritage as the technology of choice for corporations building XML processing applications. Designed from the ground up as a single, integrated environment, applications can be developed in OmniMark significantly faster than in any other technology. OmniMark can handle enormous content volumes of diverse types from multiple streams and perform complex content processing tasks with immense speed. For over a decade, many of the world's leading organizations in industries such as publishing, government, telecommunications, aerospace and automotive have profited from using OmniMark to power their content engineering processes.

Quite a large collection on xml and non-xml relates technical resources. A very exhaustive list can be found here.